Eyeglass/contact lens power determining system, and its method

ABSTRACT

A system and method for determining an eyeglass/contact lens power is provided, which can determine the power of an eyeglass/contact lens that is suitable for an individual. The eyeglass/contact lens power determination system ( 20 ) according to the present invention comprises inputting means ( 202 ) for entering information on the condition of a subject&#39;s eye, means ( 204 ) for determining an optical eyeball model corresponding to the information on the eye condition entered through the inputting means ( 202 ), and means ( 218 ) for selecting a lens power for verifying the focal power of an eyeglass/contact lens worn by the subject using the optical eyeball model determined by the optical eyeball model determining means to select a lens power.

TECHNICAL FIELD

[0001] The present invention relates to systems and methods fordetermining eyeglass/contact lens powers. In particular, the presentinvention relates to a system and method for determiningeyeglass/contact lens powers, the system and method being preferablyused with a remote subjective vision measurement system in which anyonecan make subjective vision measurements or determine his or hereyeglass/contact lens power over networks.

BACKGROUND ART

[0002] Conventionally known as means for selecting eyeglass lenses aremethods which utilize eyeball models. As the eyeball models, well knownare the Gullstrand eyeball model and the Le-Grand eyeball model.

[0003] These eyeball models have been used entirely for the design andevaluation of eyeglass lenses. For the design of eyeglass lenses, onestandard model prepared as an optical eye model would make it possibleto design lenses having various powers for standard eyes. This issufficiently enough for the design irrespective of the eye structure ofa person because he/she can select among eyeglass lenses prepared everypower of 0.25 D by actually wearing them, thereby ensuring that he/shefinds eyeglass lenses suitable for correction. That is, there is aflexibility of selection.

[0004] These days, on the other hand, to measure uncorrected orcorrected vision, one goes to see an ophthalmologist or has his/hersharpness of vision measured at eyeglass shops using their optometers.

[0005] Recently, for example, virtual malls are available over networkssuch as the Internet; however, any of the eyeglass shops available inthese virtual malls provides no system for measuring the uncorrected andcorrected vision on an on-line basis.

[0006] However, to solely determine the power of eyeglass lensessuitable for the eyes of an individual, an optical eyeball model such asthe eyeball model assumed to be commonly applicable to everyone wouldcause significant error in optical calculation thereby making thedetermination impossible. The determination can be made only byconstructing an optical eyeball model for each person.

[0007] Using the conventional eyeball models, as they are, will raisethe following problems. That is,

[0008] Since the conventional eyeball model is based on measurementsmade on eyes of people from Europe and the United States, they cannot beused for constructing a model having values close to those obtained bymeasuring living eyes of other races, e.g., Japanese people. Forexample, Japanese have a smaller radius of curvature of the cornea thando people from Europe and the United States.

[0009] A model is prepared based on an average of measurements.

[0010] Literatures show such data that the depth of the anterior chamberof the eye varies with age or the length of the eye axis is correlatedwith the degree of myopia for low degrees of nearsightedness. Thus, itis apparently necessary to construct an optical eyeball model accordingto the age and the degree of myopia of each individual.

[0011] Although the lens of the eye has a refractive index unevenlydistributed, the average refractive index is used. The simplified doublestructure provided to the lens of the eye causes a significant error intracking rays of light.

[0012] On the other hand, where difficulty is found in visiting medicalcare providers or eyeglass shops such as due to the time required andthe distance traveled for the visit, there has been a need forimplementing a system which enables one to remotely measure his/hersharpness of vision over the Internet.

[0013] In particular, one's currently wearing eyeglasses or contactlenses may provide more blurred viewing than before. In this case, itwould be very convenient if one can remotely measure his/her uncorrectedand corrected vision in order to determine whether he/she needs to buynew eyeglasses or contact lenses.

[0014] It is therefore a principal object of the present invention toprovide a system and method for determining an eyeglass/contact lenspower suitable for an individual.

DISCLOSURE OF THE INVENTION

[0015] The invention set forth in claim 1 provides a system fordetermining an eyeglass/contact lens power, the system comprising:inputting means for entering information on a condition of a subject'seye; means for determining an optical eyeball model corresponding to theinformation on the eye condition entered through the inputting means;and means for selecting a lens power for verifying a focal power of aneyeglass/contact lens worn by the subject using the optical eyeballmodel determined by the optical eyeball model determining means. In thiscase, an optical eyeball model unique to the subject is constructed toselect a lens power using the optical eyeball model. This makes itpossible to select the lens power of the eyeglass/contact lens which isoptimally suitable for the subject.

[0016] The invention set forth in claim 2 provides the system fordetermining an eyeglass/contact lens power according to claim 1, whereinthe inputting means includes means for displaying an astigmatic axismeasurement chart to measure an astigmatic axis. This makes it possibleto know the astigmatic axis of the subject.

[0017] The invention set forth in claim 3 provides the system fordetermining an eyeglass/contact lens power according to claim 1 or 2,wherein the inputting means includes means for displaying a far pointvision measurement chart to measure far point vision. This makes itpossible to know the far point vision of the subject.

[0018] The invention set forth in claim 4 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 3, wherein the inputting means includes means for displayinga near point distance measurement chart to measure a near pointdistance. This makes it possible to know the near point distance of thesubject.

[0019] The invention set forth in claim 5 provides the system fordetermining an eyeglass/contact lens power according to claim 3 or 4,wherein the inputting means has means for calculating a far pointdistance from the far point vision measured. In this case, the far pointdistance is calculated from the far point vision to determine an opticaleyeball model in accordance with the resulting value. This makes itpossible for the subject to select the lens power of his/hereyeglass/contact lens, which is optimally suitable for the subject, bymeasuring the far point vision without actually measuring the far pointdistance. This preferably allows the subject to select the lens power ofhis/her eyeglass/contact lens in a small room or the like.

[0020] The invention set forth in claim 6 provides the system fordetermining an eyeglass/contact lens power according to claim 5, whereinthe inputting means has means for determining an approximate lens powerfrom the far point distance calculated. In this case, the age, the nearpoint distance, and the far point distance of the subject are entered tothereby determine his/her optical eyeball model. This makes it possiblefor the subject to select the lens power of his/her eyeglass/contactlens, which is optimally suitable for the subject, by entering the age,the near point distance, and the far point distance of the subject.

[0021] The invention set forth in claim 7 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 6, wherein the optical eyeball model simulates each layer ofan anterior cortex, a nucleoplasm, and a posterior cortex of the lens ofthe eye using a combination of plurality of lenses, respectively. Inthis case, it is possible to construct an optical eyeball model that issimilar to the actual eyeball structure. This also makes it possible toselect the lens power of the eyeglass/contact lens which is suitable forthe subject.

[0022] The invention set forth in claim 8 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 7, wherein the optical eyeball model has a characteristicthat a refractive index of each of the lenses simulating the lens of theeye is decreased with a distance from the center of the lens. In thiscase, it is also possible to construct an optical eyeball model that issimilar to the actual eyeball structure. This also makes it possible toselect the lens power of the eyeglass/contact lens which is suitable forthe subject.

[0023] The invention set forth in claim 9 provides the system fordetermining an eyeglass/contact lens power according to claim 8, whereinthe optical eyeball model has a refractive index distributioncharacteristic that the refractive index of each of the lensessimulating the lens of the eye is expressed by (a refractive index atthe center of the lens)−((the square of a straight distance from thelens center)/(a refractive index distribution coefficient)). In thiscase, it is also possible to construct an optical eyeball model that issimilar to the actual eyeball structure. This also makes it possible toselect the lens power of the eyeglass/contact lens which is suitable forthe subject.

[0024] The invention set forth in claim 10 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 7 to 9, wherein the refractive index distribution coefficient ofeach lens simulating the lens of the eye is decreased with the distancefrom the center of the plurality of lenses in a direction of the opticalaxis simulating the lens of the eye to the direction of the opticalaxis. In this case, it is also possible to construct an optical eyeballmodel that is similar to the actual eyeball structure. This also makesit possible to select the lens power of the eyeglass/contact lens whichis suitable for the subject.

[0025] The invention set forth in claim 11 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 7 to 10, wherein the optical eyeball model calculates opticaldimensions using a power distribution coefficient describing thedistribution of accommodation power per unit length of each lenssimulating the lens of the eye. In this case, it is also possible toconstruct an optical eyeball model that takes into account theaccommodation power of the actual eyeball. This also makes it possibleto select the lens power of the eyeglass/contact lens which is suitablefor the subject.

[0026] The invention set forth in claim 12 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 11, wherein the means for determining an optical eyeballmodel determines a starting optical eyeball model in accordance with anage of the subject and information on the eye such as an approximatelens power. In this case, an optical eyeball model is selected inaccordance with the age of the subject and the information on the eyesuch as the approximate lens power to thereby select the lens power ofthe eyeglass/contact lens which is optimally suitable for the subject.This makes it possible to select the lens power of the eyeglass/contactlens, which is optimally suitable for the subject, only by the subjectentering his/her age and information required for calculating theapproximate lens power or the like.

[0027] The invention set forth in claim 13 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 12, wherein the means for determining an optical eyeballmodel has means for verifying validity of the optical eyeball model at agiven accommodation point between the near point distance and the farpoint distance of the subject entered. In this case, determined is anoptical eyeball model which more closely simulates the eyeball of thesubject. This also makes it possible to select the lens power of theeyeglass/contact lens which is suitable for the subject.

[0028] The invention set forth in claim 14 provides the system fordetermining an eyeglass/contact lens power according to claim 13,wherein the given accommodation point between the near point distanceand the far point distance of the subject entered includes anaccommodation midpoint calculated from the near point distance and thefar point distance of the subject. This makes it possible to equallydistribute the accommodation power to the respective strained andrelaxed sides.

[0029] The invention set forth in claim 15 provides the system fordetermining an eyeglass/contact lens power according to claim 13 or 14,wherein the means for determining an optical eyeball model employs aradius of curvature and an eccentricity of an aspherical surface asparameters to perform automatic aberration correction processing. Inthis case, the automatic aberration correction processing is performedin a short period of time. This makes it possible to quickly select thelens power of the eyeglass/contact lens which is optimally suitable forthe subject.

[0030] The invention set forth in claim 16 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 15, wherein the means for determining an optical eyeballmodel includes means for verifying validity of the optical eyeball modelat an accommodation limit on a near point side and/or a far point side.This also makes it possible to select the lens power of theeyeglass/contact lens which is suitable for the subject.

[0031] The invention set forth in claim 17 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 16, wherein the means for determining an optical eyeballmodel displays an image of the optical eyeball model determined. Thismakes it possible for the subject to view how his/her optical eyeballmodel has been determined.

[0032] The invention set forth in claim 18 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 17, wherein the means for selecting a lens power has afunction to verify the focal power at a single distance or a pluralityof distances defined according to usage. In this case, the focal poweris calculated at three distances according to actual usage. This allowsthe subject to readily determine whether the selected lens is suitablefor his/her usage.

[0033] The invention set forth in claim 19 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 18, wherein the means for selecting a lens power has afunction to verify by comparison the focal power of the optical eyeballmodel for an uncorrected eye. In this case, the focal conditions of theuncorrected and corrected eyes are verified by comparison, therebymaking clear what kind of changes may occur when the subject wears theeyeglasses or the contact lenses. This also makes it possible toaccurately select appropriate lenses.

[0034] The invention set forth in claim 20 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 19, wherein the means for selecting a lens power includesmeans for calculating a sharpness score indicative of the degree ofblurring in a visual image viewed by an optical eyeball model. In thiscase, the focal conditions of the uncorrected and corrected eyes areverified by comparison, thereby making clear what kind of changes haveoccurred. This also makes it possible to accurately select appropriatelenses.

[0035] The invention set forth in claim 21 provides the system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 20, wherein the means for selecting a lens power includesmeans for presenting a simulated visual image viewed by the opticaleyeball model. In this case, it is possible to view and check directlyon a screen the degree of blurring in an image viewed by the subject.This allows the subject to easily select lenses.

[0036] The invention set forth in claim 22 provides a method fordetermining an eyeglass/contact lens power, the method comprising stepsof collecting information on the conditions of an eye of a subject;determining an optical eyeball model corresponding to the information onthe conditions of the eye collected in the collecting step; andselecting a lens power by verifying a focal power of an eyeglass/contactlens worn by the subject using the optical eyeball model determined inthe step for determining an optical eyeball model. In this case, anoptical eyeball model unique to the subject is constructed to select alens power using the optical eyeball model. This makes it possible toselect the lens power of the eyeglass/contact lens which is optimallysuitable for the subject.

[0037] The invention set forth in claim 23 provides the method fordetermining an eyeglass/contact lens power according to claim 22,wherein the collecting step includes a step of displaying an astigmaticaxis measurement chart to measure an astigmatic axis. This makes itpossible to know the astigmatic axis of the subject.

[0038] The invention set forth in claim 24 provides the method fordetermining an eyeglass/contact lens power according to claim 22 or 23,wherein the collecting step includes a step of displaying a far pointvision measurement chart to measure far point vision. This makes itpossible to know the far point vision of the subject.

[0039] The invention set forth in claim 25 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 24, wherein the collecting step includes a step ofdisplaying a near point distance measurement chart to measure a nearpoint distance. This makes it possible to know the near point distanceof the subject.

[0040] The invention set forth in claim 26 provides the method fordetermining an eyeglass/contact lens power according to claim 24 or 25,wherein the collecting step has a step of calculating a far pointdistance from the far point vision measured. This makes it possible forthe subject to select the lens power of his/her eyeglass/contact lens,which is optimally suitable for the subject, by measuring the far pointvision without actually measuring the far point distance. Thispreferably allows the subject to select the lens power of his/hereyeglass/contact lens in a small room or the like.

[0041] The invention set forth in claim 27 provides the method fordetermining an eyeglass/contact lens power according to claim 26,wherein the collecting step has a step of determining an approximatelens power from the far point distance calculated. In this case, theage, the near point distance, and the far point distance of the subjectare entered to thereby determine his/her optical eyeball model. Thismakes it possible for the subject to select the lens power of his/hereyeglass/contact lens, which is optimally suitable for the subject, byentering the age, the near point distance, and the far point distance ofthe subject.

[0042] The invention set forth in claim 28 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 27, wherein the optical eyeball model simulates each layerof an anterior cortex, a nucleoplasm, and an posterior cortex of thelens of the eye using a combination of plurality of lenses,respectively. In this case, it is possible to construct an opticaleyeball model that is similar to the actual eyeball structure. This alsomakes it possible to select the lens power of the eyeglass/contact lenswhich is suitable for the subject.

[0043] The invention set forth in claim 29 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 28, wherein the optical eyeball model has a characteristicthat a refractive index of each of the lenses simulating the lens of theeye is decreased with a distance from the center of the lens. In thiscase, it is also possible to construct an optical eyeball model that issimilar to the actual eyeball structure. This also makes it possible toselect the lens power of the eyeglass/contact lens which is suitable forthe subject.

[0044] The invention set forth in claim 30 provides the method fordetermining an eyeglass/contact lens power according to claim 29,wherein the optical eyeball model has a refractive index distributioncharacteristic that the refractive index of each of the lensessimulating the lens of the eye is expressed by (a refractive index atthe center of the lens)−((the square of a straight distance from thelens center)/(a refractive index distribution coefficient)). In thiscase, it is also possible to construct an optical eyeball model that issimilar to the actual eyeball structure. This also makes it possible toselect the lens power of the eyeglass/contact lens which is suitable forthe subject.

[0045] The invention set forth in claim 31 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 28 to 30, wherein the refractive index distribution coefficientof each lens simulating the lens of the eye is decreased with thedistance from the center of the plurality of lenses in a direction ofthe optical axis simulating the lens of the eye to the direction of theoptical axis. In this case, it is also possible to construct an opticaleyeball model that is similar to the characteristics of the actualeyeball. This also makes it possible to select the lens power of theeyeglass/contact lens which is suitable for the subject.

[0046] The invention set forth in claim 32 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 28 to 31, wherein the optical eyeball model calculates opticaldimensions using a power distribution coefficient describing thedistribution of accommodation power per unit length of each lenssimulating the lens of the eye. In this case, it is also possible toconstruct an optical eyeball model that takes into account theaccommodation power of the actual eyeball. This also makes it possibleto select the lens power of the eyeglass/contact lens which is suitablefor the subject.

[0047] The invention set forth in claim 33 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 32, wherein the step of determining an optical eyeballmodel determines a starting optical eyeball model in accordance with anage of the subject and information on the eye such as an approximatelens power. In this case, an optical eyeball model is selected inaccordance with the age of the subject and the information on the eyesuch as the approximate lens power to thereby select the lens power ofthe eyeglass/contact lens which is optimally suitable for the subject.This makes it possible to select the lens power of the eyeglass/contactlens, which is optimally suitable for the subject, only by the subjectentering his/her age and information required for calculating theapproximate lens power or the like.

[0048] The invention set forth in claim 34 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 33, wherein the step of determining an optical eyeballmodel has a step of verifying validity of the optical eyeball model at agiven accommodation point between the near point distance and the farpoint distance of the subject entered. In this case, determined is anoptical eyeball model which more closely simulates the eyeball of thesubject. This also makes it possible to select the lens power of theeyeglass/contact lens which is suitable for the subject.

[0049] The invention set forth in claim 35 provides the method fordetermining an eyeglass/contact lens power according to claim 34,wherein the given accommodation point between the near point distanceand the far point distance of the subject entered includes anaccommodation midpoint calculated from the near point distance and thefar point distance of the subject. This makes it possible to equallydistribute the accommodation power to the respective strained andrelaxed sides.

[0050] The invention set forth in claim 36 provides the method fordetermining an eyeglass/contact lens power according to claim 34 or 35,wherein the step of determining an optical eyeball model employs aradius of curvature and an eccentricity of an aspherical surface asparameters to perform automatic aberration correction processing. Inthis case, the automatic aberration correction processing is performedin a short period of time. This makes it possible to quickly select thelens power of the eyeglass/contact lens which is optimally suitable forthe subject.

[0051] The invention set forth in claim 37 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 36, wherein the step of determining an optical eyeballmodel includes a step of verifying validity of the optical eyeball modelat an accommodation limit on a near point side and/or a far point side.This also makes it possible to select the lens power of theeyeglass/contact lens which is suitable for the subject.

[0052] The invention set forth in claim 38 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 37, wherein the step of determining an optical eyeballmodel displays an image of the optical eyeball model determined. Thismakes it possible for the subject to view how his or her optical eyeballmodel has been determined.

[0053] The invention set forth in claim 39 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 38, wherein the step of selecting a lens power has a stepof verifying the focal power at a single distance or a plurality ofdistances defined according to usage. In this case, the focal power iscalculated at three distances according to actual usage. This allows thesubject to readily determine whether the selected lens is suitable forhis/her usage.

[0054] The invention set forth in claim 40 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 39, wherein the step of selecting a lens power has a stepof verifying by comparison the focal power of the optical eyeball modelfor an uncorrected eye. In this case, the focal conditions of theuncorrected and corrected eyes are verified by comparison, therebymaking clear what kind of changes may occur when the subject wears theeyeglasses or the contact lenses. This also makes it possible toaccurately select appropriate lenses.

[0055] The invention set forth in claim 41 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 40, wherein the step of selecting a lens power includes astep of calculating a sharpness score indicative of the degree ofblurring in a visual image viewed by an optical eyeball model. In thiscase, the focal conditions of the uncorrected and corrected eyes areverified by comparison, thereby making clear what kind of changes haveoccurred. This also makes it possible to accurately select appropriatelenses.

[0056] The invention set forth in claim 42 provides the method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 41, wherein the step of selecting a lens power includes astep of presenting a simulated visual image viewed by the opticaleyeball model. In this case, it is possible to view and check directlyon a screen the degree of blurring in an image viewed by the subject.This allows the subject to easily select lenses.

[0057] The aforementioned objects, other objects, features, andadvantages of the present invention will be better understood from thefollowing detailed descriptions to be made with reference to thedrawings in accordance with the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

[0058]FIG. 1 is a view illustrating an exemplary configuration of aremote subjective vision measurement system comprising aneyeglass/contact lens power determination server incorporating aneyeglass/contact lens power determination system according to anembodiment of the present invention;

[0059]FIG. 2 is a cross-sectional pictorial view illustrating aneyeball;

[0060]FIG. 3 is a cross-sectional pictorial view illustrating an opticaleyeball model;

[0061]FIG. 4 is an explanatory pictorial view illustrating therefractive index distribution of each of lenses simulating the lens ofthe eye;

[0062]FIG. 5 is a view showing the relationship between the age and theaccommodation power of the eye;

[0063]FIG. 6 is a pictorial view illustrating an example of anastigmatic axis determination chart;

[0064]FIG. 7 is a view showing a processing flow of an eyeglass/contactlens power determination system;

[0065]FIG. 8 is a schematic view illustrating a starting optical eyeballmodel;

[0066]FIG. 9 is a pictorial view illustrating a method for representingan image presented;

[0067]FIG. 10 show pictorial views illustrating images viewed before andafter correction;

[0068]FIG. 11 is a view illustrating a processing flow of an optometeraccording to an embodiment of the present invention;

[0069]FIG. 12 is a view illustrating an example of a representation ofan individual information input window;

[0070]FIG. 13 is a view illustrating an example of a representation of awearing condition input window;

[0071]FIG. 14 is a view illustrating an example of a representation ofan explanatory window for an astigmatic axis determination;

[0072]FIG. 15 is a view illustrating an example of a representation ofan astigmatic axis determination window;

[0073]FIG. 16 is a view illustrating an example of a representation ofan explanatory window for a far point vision measurement;

[0074]FIG. 17 is a view illustrating an example of a representation of afar point vision measurement window;

[0075]FIG. 18 is a view illustrating an example of a representation ofan explanatory window for a near point distance measurement;

[0076]FIG. 19 is a view illustrating an example of a representation of anear point distance measurement window; and

[0077]FIG. 20 is a view illustrating an example of a configuration of aneural network for calculating a far point distance.

BEST MODE FOR CARRYING OUT THE INVENTION

[0078]FIG. 1 is a view illustrating an exemplary configuration of aremote subjective vision measurement system comprising aneyeglass/contact lens power determination server incorporating aneyeglass/contact lens power determination system according to anembodiment of the present invention.

[0079] As shown in FIG. 1, the remote subjective vision measurementsystem 10 comprises hardware of user clients 1 and an electronic servicecenter 2. These are physically connected to each other via networks.

[0080] The following descriptions will be given assuming that thenetwork connecting between the user clients 1 and the electronic servicecenter 2 is the Internet.

[0081] The remote subjective vision measurement system 10, comprisingthe electronic service center 2, can construct an optical eyeball modelunique to a subject to determine the optimal power for the subject inaccordance with the age and wearing conditions entered at the userclient 1 and the vision measurement data indicative of the degree ofnearsightedness, farsightedness and astigmatism.

[0082] The electronic service center 2 comprises an eyeglass/contactlens power determination server 20, which has inputting means 202,optical eyeball model determination means 204, model validity verifyingmeans 206, optical eyeball dimension accommodation range defining means208, optical eyeball model image generating means 210, optical eyeballmodel focal power verifying means 212, visual image generating means214, sharpness score generating means 216, lens power selecting means218, outputting means 220, user information management means 230, anddatabase management means 232, and a WWW (World Wide Web) server 30.

[0083] More specifically, the electronic service center 2 comprisesinformation processing devices including, for example, personalcomputers, workstations, and servers.

[0084] The databases controlled by the database management means 232 arestored in a storage device such as a magnetic disc device or an opticaldisc device.

[0085] The electronic service center 2 is connected to the user clients1 via a wide area computer network (the Internet).

[0086] The WWW server 30 provides a homepage that is used as aninterface across which the user client 1 accesses the databasemanagement means 232 or the like in the electronic service center 2.

[0087] Furthermore, the WWW server 30 has user authentication means (notshown) which uses a password/identifier (ID) to verify whether an userhas been authorized to have a right to register with or request theviewing of the databases managed by the database management means 232.

[0088] The lens power selecting means 218 verifies the opticalperformance of an eyeglass/contact lens worn by a subject to select thelens power.

[0089] The inputting means 202 is designed to receive information on theeyes of a subject such as the wearing conditions, the age, the nearpoint distance, and the far point distance of the subject. Furthermore,the inputting means 202 comprises astigmatic axis measuring means fordisplaying an astigmatic axis measurement chart to measure theastigmatic axis; far point vision measuring means for displaying a farpoint vision measurement chart used with the measurement of far pointvision to measure a far point distance; near point distance measuringmeans for displaying a near point distance measurement chart to measurea near point distance; far point distance calculating means forcalculating a far point distance from the far point vision; and meansfor determining an approximate lens power from the far point distance orthe like.

[0090] The optical eyeball model determination means 204 is designed todetermine a starting optical eyeball model in accordance with the age ofa subject and information on the eye such as the approximate lens power.The optical eyeball model determination means 204 is designed todetermine an optical eyeball model in accordance with such eyeballoptical dimensions that the focal power of the eyeball of a subject isoptimized at the accommodation midpoint calculated from the near pointdistance and the far point distance of the subject. This embodiment isdesigned to determine the optical eyeball model at the accommodationmidpoint based on the fact that a condition can be provided, in whichthe eyeball is strained to its limit or relaxed to its limit, by equallydistributing the accommodation power of the eyeball of the subject tothe strained side or the relaxed side.

[0091] Now, the optical eyeball model to be constructed according tothis embodiment will be explained below. In the optical eyeball model, ahuman eye and a lens such as an eyeglass/contact lens, as shown in FIG.2, are configured as an optical system numerical model from a pluralityof lenses as shown in FIG. 3. As shown in FIG. 3, the optical eyeballmodel comprises light-ray refracting elements of the eyeball such as thecornea, the anterior chamber, the lens of the eye, and the vitreousbody, and the retina or an optically evaluated surface. An opticaleyeball model is constructed with respect to these elements inaccordance with the following optical dimensions.

[0092] Eyeglass/contact lens: the radius of curvature R1 of the lensfront surface, the thickness, the refractive index, and the radius ofcurvature R2 of the lens rear surface Cornea: the radius of curvature R3of the front surface, the thickness, the refractive index, and theradius of curvature R4 of the rear surface

[0093] Anterior chamber: the thickness and the refractive index

[0094] Lens of the eye: the radius of curvature (the radii of curvatureR5, R6, R7, R8, R9, R10, and R11 on each boundary surface of lenses insix layers simulating the anterior cortex) and the thickness of theanterior cortex; the radius of curvature (the radii of curvature R11,R12, R13, R14, R15, R16, R17, R18, and R19 on each boundary surface oflenses in eight layers simulating the nucleoplasm) and the thickness ofthe nucleoplasm; and the radius of curvature (the radii of curvatureR19, R20, R21, R22, R23, R24, and R25 on each boundary surface of lensesin six layers simulating the posterior cortex) and the thickness of theposterior cortex and their respective refractive indices

[0095] Vitreous body: the refractive index and the thickness

[0096] Retina: Radius of curvature R26

[0097] The aforementioned optical dimensions are different from eachother depending on the age and the accommodation capability of the eyeof each individual. However, in this embodiment, an optical eyeballmodel is pre-constructed as a standard pattern with respect to valuesfrom living body measurement data on Japanese people and those fromliterature data.

[0098] Now, shown below is an example of literature data applicable tothe construction of an optical eyeball model.

[0099] (i) Concerning the Depth of the, Anterior Chamber

[0100] According to “Study on the depth of anterior chamber” by KatsuoAizawa, Japanese Ophthalmological Society Journal Vol.62, No. 11 (1958),the relationship between the depth of the anterior chamber and the agevaries as follows:

[0101] 3.66 mm for ages from 8 to 15,

[0102] 3.71 mm for ages from 16 to 30,

[0103] 3.51 mm for ages from 31 to 51, and

[0104] 3.18 mm for ages from 51 to 77.

[0105] That is, the study tells that the depth of the anterior chambertends to gradually increase as the body grows from the youth and reachthe maximum level when the body has grown up, thereafter graduallydecrease as the body deteriorates.

[0106] (ii) Concerning the Length of the Eye Axis

[0107] According to “Study No. 1 on the essence of nearsightedness” byTsutomu Sato, et al, Japanese Ophthalmological Society Journal Vol.63,No. 7 (1959), for the low degree of nearsightedness, the length of theeye axis gradually increases as the degree of myopia becomes higher,showing a strong correlation therebetween.

[0108] (iii) Concerning the Weight of the Lens of the Eye

[0109] According to “The eye” by Davson Hugh (1909-) and Graham L. T.Jr., New York; London Academic Press, the weight of the lens of the eyeonly increases with advancing age as follows:

[0110] 174 mg for ages from 20 to 39,

[0111] 204 mg for ages from 40 to 59, and

[0112] 266 mg for ages from 80 to 99.

[0113] (iv) Concerning the Thickness and Diameter of the Lens of the Eye

[0114] According to Complete Collection of New Clinical Ophthalmology3A, by Hiroshi Ichikawa, et al, 1993, KANEHARA & CO., LTD, the thicknessand diameter of the lens of the eye increases with advancing age.

[0115] The optical eyeball model that has been constructed by applyingthe values from the aforementioned literatures and those of the livingbody measurement data is used as the starting optical eyeball model. Thestarting optical eyeball model is not constructed for the combinationsof all ages and approximate lens powers, but with attention being givento the fact that the starting optical eyeball model has generally commoneye characteristics for the same age and approximate lens power, such anoptical eyeball model is pre-constructed, which has a median value ineach age class represented on the vertical axis and a median value ineach approximate lens power class represented on the horizontal axis.The vertical axis representing M classes and the horizontal axisrepresenting N classes allow for constructing M by N starting opticaleyeball models. That is, employed is a table in which the vertical axisrepresents the age class (e.g., at five year intervals up to twentyyears of age, and at 6 or 10 year intervals for 20 years of age or more)and the horizontal axis represents the approximate lens power (e.g., atintervals of 1.0 D). With this table, such a starting optical eyeballmodel is pre-constructed at a combination of median values in each class(e.g., the 35 years of age and the lens power of the amount ofcorrection required being −2.5 D). Now, some values of the opticaldimensions from the starting eyeball model constructed according to thisembodiment are shown as an example.

[0116] Table 1 shows the values indicative of the depth of the anteriorchamber applied from the correlation between the age and the approximatelens power. TABLE 1 Approximate lens power (D) AGE CLASS 0 −2 −4 −618(10-26) 3.58 3.75 3.87 3.98 36(27-44) 3.42 3.57 3.70 3.80 47(45-49)3.10 3.25 3.37 3.44 55(50-59) 2.94 3.10 3.23 3.31

[0117] Table 2 shows the values indicative of the length of the eye axisapplied from the correlation between the age and the approximate lenspower. TABLE 2 Approximate lens power (D) AGE CLASS 0 −2 −4 −6 18(10-26)23.50 24.40 25.10 26.02 36(27-44) 23.70 24.50 25.20 26.00 47(45-49)23.70 24.50 25.20 26.00 55(50-59) 23.70 24.50 25.20 26.00

[0118] Since no significant change may appear in the shape of the eye at60 years of age or more, this embodiment was designed to use the samevalues as those of the age class for 55 (50 to 59) years of age.

[0119] In accordance with the contents such as of the data from theaforementioned literatures, this embodiment also introduced thefollowing parameters for each layer of the lens of the eye to beconstructed by the optical eye model determining means. Now, anexplanation is given below to the parameters introduced for the opticaldimensions corresponding to the lens of the eye in the optical eyeballmodel.

[0120] The aspherical surface of the lens at each layer of the lens ofthe eye to be constructed by optical eyeball model constructing means isdetermined as expressed in the following equation. $\begin{matrix}{Z = {\frac{{CY}^{2}}{1 + \sqrt{1 - {\left( {K + 1} \right)C^{2}Y^{2}}}} + {A_{4}Y^{4}} + {A_{6}Y^{6}} + {A_{8}Y^{8}} + \ldots}} & {{Equation}\quad 1}\end{matrix}$

[0121] In equation 1, R is the radius of the reference sphericalsurface, C is 1/R, and K is the eccentricity. Here, the asphericalsurface coefficients A₄, A₆, A₈, . . . , are all set to zero because thefirst term sufficiently represents the shape of the lens.

[0122] Furthermore, each lens simulating the lens of the eye is designedto have an uneven distribution of refractive indices exhibitingdifferent refractive indices depending on the portion. As shown in FIG.4, the following equation represents the refractive index nr that isapart by distance r from the lens center of each lens in a directionperpendicular to the optical axis:

n _(r) =n _(r0) −δn(r)   Equation 2

[0123] In equation 2, n₀ is the refractive index at the lens center andδn(r) is the amount of refractive index decreased with the distance fromthe lens center, δn(r) being expressed by the following equation:

δn(r)=r ² /K _(s)   Equation 3

[0124] In equation 3, K_(s) is the refractive index distributioncoefficient, and its value represents the degree of unevenness in therefractive index distribution of the lens. The value of the coefficientis determined for each lens in accordance with the data or the like ofthe aforementioned literatures. As shown in Table 3, with attentionbeing given to the fact that the central portion of the lens of the eyehas higher refractive indices, the lenses closer to the central portionin the direction of the optical axis of the plurality of lensessimulating the lens of the eye were designed to have higher values.TABLE 3 Refractive index Lens distribution coefficient  R5-R6 250  R8-R9290 R11-R12 325 R13-R14 360 R17-R18 400 R19-R20 360 R22-R23 300

[0125] As described above, for example, when the lens with a refractiveindex distribution coefficient K_(s) of 200 has a refractive indexn_(r0) of 1.410 at the lens center, the refractive index of a portionapart by 1.0 mm from the lens center is 1.405 and that of a portionapart by 1.5 mm therefrom is 1.399.

[0126] Furthermore, as the eye to be strained or relaxed to therebyaccommodate the refractive power, the optical eyeball model constructingmeans calculates optical dimensions using the power distributioncoefficient describing the distribution of the accommodation power perunit length of each lens simulating the lens of the eye. Thus, theoptical eyeball model constructing means determines the opticaldimensions to simulate the lens of the eye in its strained and relaxedconditions. In this embodiment, the refractive index distributioncoefficient K_(s), the aspherical surface coefficient K, and the radiusof curvature R were to vary the optical dimensions of each lens usingthe power distribution coefficient. Now, this will be explained belowwith reference to an example.

[0127] It is to be understood that accommodation can be performed froman accommodation midpoint to a −aD side (a near point distance) or to a+aD side (a far point distance) when the optical dimensions of theoptical eyeball model have been determined at the accommodationmidpoint. As used herein, D is the diopter the value of which isexpressed by the reciprocal of the distance (measured in meters) from areference point of the lens to the focal point. When accommodation isperformed by bD to the relaxed side, the lens dimensions of the lens ofthe eye of the optical eyeball model are determined using the powerdistribution coefficient to multiply the values of the refractive indexdistribution coefficient K_(s), the aspherical surface coefficient K,and the radius of curvature R at the accommodation midpoint by (1+×b/a),thereby determining an optical eyeball model that simulates the eyeballin its relaxed condition. Conversely, for accommodation being performedby bD to the strained side, the values of the optical dimensions at theaccommodation midpoint are multiplied by (1−×b/a), thereby determiningan optical eyeball model that simulates the eyeball in its strainedcondition. As described above, the starting optical eyeball modelemploys an optical eyeball model which represents any degree of relaxingor strain by varying the aforementioned optical dimensions of the lensof the eye depending on the accommodation power.

[0128] By way of example, the lens power at the accommodation midpointis −5.02 D when the lens power of the subject is −10.2 D at the nearpoint distance and −0.2 D at the far point distance. In this example,suppose that the refractive index distribution coefficient K_(s) of eachlens at the accommodation midpoint takes the value indicated at thesecond column from the left in Table 4. In this case, the refractiveindex distribution coefficients K_(s) on the strained and relaxed sidestake on the values shown in Table 4 from the values of of each lens andthe amount of accommodation. TABLE 4 Accommodation midpoint Relaxed-sideStrained-side refractive index refractive index refractive indexdistribution distribution distribution Lens coefficient K_(s) αcoefficient K_(s) coefficient K_(s)  R5-R6 250 0.400 350.0 150.0  R8-R9290 0.388 402.5 177.5 R11-R12 325 0.385 450.0 200.0 R13-R14 360 0.382497.5 222.5 R17-R18 400 0.375 550.0 250.0 R19-R20 360 0.360 489.6 230.4R22-R23 300 0.333 399.9 200.1

[0129] On the other hand, the aspherical surface coefficient K takes onthe values shown in Table 5. TABLE 5 Accommodation midpoint Relaxed-sideStrained-side Boundary aspherical aspherical aspherical surface surfacesurface surface No. coefficient K α coefficient K coefficient K R5 2.0000.700 3.400 0.600 R8 −0.600 0.700 −1.020 −0.180 R11 −0.800 0.700 −1.360−0.240 R13 −1.000 0.700 −1.700 −0.300 R17 −1.200 0.700 −2.040 −0.360 R19−1.100 0.700 −1.870 −0.330 R22 −1.000 0.700 −1.700 −0.300 R25 −0.2000.700 −0.340 −0.060

[0130] The reference spherical surface radius R takes on the valuesshown in Table 6.

[0131] (Remainder left blank) TABLE 6 Accommodation Strained-sidemidpoint Relaxed-side reference Boundary reference reference sphericalsurface spherical spherical surface No. surface radius R α surfaceradius R radius R R5 7.122 −0.295 10.102 5.500 R8 5.308 −0.299 7.5724.086 R11 4.230 −0.301 6.052 3.251 R13 3.622 −0.341 5.496 2.701 R17−3.346 −0.240 −4.400 −2.699 R19 −3.833 −0.183 −4.692 −3.240 R22 −4.634−0.144 −5.414 −4.051 R25 −5.858 −0.085 −6.402 −5.399

[0132] In this embodiment, the power distribution coefficient has beendetermined in accordance with the values of living body measurement dataon Japanese people and data from the literatures.

[0133] The model validity verifying means 206 verifies the validity ofthe optical eyeball model at the midpoint and at the accommodationlimits on the near point and the far point sides.

[0134] The optical eyeball dimension accommodation range defining means208 is designed to define the range of eyeball accommodation at theaccommodation midpoint and display the image of an optical eyeball modelthat defines the range of eyeball accommodation at the accommodationmidpoint.

[0135] On the other hand, the optical eyeball model focal powerverifying means 212 verifies the focal power of the optical eyeballmodels at the three distances determined according to usage. Forexample, the three distances defined according to usage include 0.3 mm(a near distance) assuming reading or desk work, 0.5 to 0.6 m(intermediate distance) assuming work at personal computers, and 5 m(far distance) assuming the driving of cars. On the other hand, theoptical eyeball model focal power verifying means 212 has a function toverify by comparison the focal power of the optical eyeball model of anuncorrected eye.

[0136] The visual image generating means 214 generates visual imagesviewed by the subject before and/or after the correction by means of aneyeglass/contact lens.

[0137] The sharpness score generating means 216 derives the sharpnessscore of the viewing by the subject before and/or after the correctionby means of an eyeglass/contact lens.

[0138] The user client 1 is a terminal for the user to utilize uponsubscribing to a vision measurement, and for example, implemented by apersonal computer.

[0139] The user client 1 is an input/output device serving as aninterface for the user, and more specifically, implemented by inputdevices such as a keyboard and a mouse and output devices such as adisplay.

[0140] The user client 1 has access means such as a WWW browser servingas an interface for communicating various types of data with the WWWserver 30 in the electronic service center 2. When the user client 1 isa personal computer, the WWW browser is implemented as a program storedin its memory.

[0141] Now, an explanation is given to the case where this system isimplemented using a homepage or the like on a network such as theInternet (a wide area computer network).

[0142] First, the electronic service center 2 uses the WWW server 30 toset up a homepage on the Internet.

[0143] The user uses the access means such as a WWW browser in the userclient 1 connected to the wide area computer network to access the userinformation management means 230 employing the homepage of theelectronic service center 2 as an interface in order to request for anvision measurement.

[0144] The electronic service center 2 allows the user authenticationmeans provided in the WWW server 30 to verify whether the user is anauthorized registered member in accordance with the password of the userand/or the user authentication information of the user identifier (ID).Thereafter, the user information management means 230 in the electronicservice center 2 writes the information, which has been transmitted torequest for registration via the wide area computer network from theuser, onto the user information database for management.

[0145] At this time, suppose that it has been found that the userutilizes the vision measurement system for the first time. In this case,a window for entering general attributes or the like is transmitted tothe user client 1 to request for the entry of data such as generalattributes such as the address, the name, the birthday, and thetelephone number, the condition of the eyes (difficulty in viewing anobject at hand), and requirements for the eyeglass. The user then inputsnecessary items at the user client 1 to transmit the items to theelectronic service center 2.

[0146] Furthermore, the user also registers his password and user memberidentifier (ID) or the like, and the user information management means230 writes the information from user onto the user information databasevia the wide area computer network for management.

[0147] The structure of each database to be managed by the databasemanagement means 232 in the electronic service center 2 is as follows.

[0148] The user information database stores user information, asinformation for identifying users, including general attributes such asthe user code, the user identifier (ID), the user password, the address,the name, the birthday, and the telephone number.

[0149] Such user information is data entered on the user informationregister window transmitted to the user client 1 by the user informationmanagement means 230, the data being provided with the user code.

[0150] It is not always necessary to register data for all the items.

[0151] The user information identifier (ID) and the password may bedetermined on the service center side in accordance with the userinformation acquired off-line or may be provided automatically upon thefirst access by the user.

[0152] The reference database for measuring vision stores data for eachuser such as the purpose of use, the near point distance, the far pointdistance, the age, the previous power, the sharpness of vision of botheyes with the previous power, the balance between the right and lefteyes with the previous power, the years of use of the previouseyeglasses, the type of contact lenses (when used together), the desiredcorrected sharpness of vision, and any eye disease affecting the vision.

[0153] A vision measurement database stores data such as uncorrectedvision, corrected vision, the distance between the pupils, thefarsighted condition correction power, the nearsighted conditioncorrection power, the date of measurement, and the power determiner.

[0154] A vision table database stores data indicative of therelationship between the power and the Landolt ring.

[0155] A nearsightedness information database manages data registeredtherewith including the degree of myopia, the relationship between thedegree of nearsightedness and the vision, the type of nearsightedness(power), and the remedy.

[0156] The nearsightedness or myopia means an eye which allows parallelbeams of light incident upon the eye to focus on a point in front of theretina without any accommodation of the eye (the far point being finitein front of the eye).

[0157] The degree of myopia is expressed with the reciprocal of the farpoint distance (e.g., as with 1/0.5=2 D for a far point distance of 50cm).

[0158] The relationship between the degree of myopia and the vision isas shown in Table 7. TABLE 7 Uncorrected Degree of Corrected visionmyopia vision 0.8 −0.5 1.2 0.5 −1.0 1.2 0.3 −1.5 1.2 0.2 −2.0 1.2 0.1−3.0 1.2 0.07 −5.0 1.2 0.06 −6.0 0.9 0.05 −7.0 0.7 0.04 −8.0 0.6 0.03−9.0 0.5

[0159] The types of myopia (power) are as follows.

[0160] Low degree of myopia (−4 D), Moderate degree of myopia (−4 D to−7 D), High degree of myopia (−7 D to −10 D), Highest degree of myopia(−10 D or more)

[0161] As a remedy for myopia, appropriate concave lenses are worn.

[0162] A farsightedness information database manages data registeredtherewith including the degree of hyperopia, the type of farsightedness,and the remedy for farsightedness.

[0163] The farsightedness or hyperopia means an eye which allowsparallel beams of light incident upon the eye to focus on a point behindthe retina without any accommodation of the eye (the far point beingfinite behind the eye).

[0164] The types of hyperopia, as expressed with their power, are asfollows.

[0165] Low degree of hyperopia (+4 D), moderate degree of hyperopia (+4D to +7 D), and high degree of hyperopia (+7 D); as a remedy forhyperopia, appropriate convex lenses are worn.

[0166] An astigmatism information database manages data registeredtherewith including the degree of astigmatism, the type of astigmatism,and the remedy. Astigmatism is a condition in which parallel beams oflight incident upon the eye do not focus on one point without anyaccommodation of the eye.

[0167] The types of astigmatism are as follows.

[0168] Regular astigmatism (symmetric unevenness on the refractivesurface)

[0169] Irregular astigmatism (different degrees of inflection in thesame light path preventing the focusing of light)

[0170] The remedies for astigmatism are as follows.

[0171] Single astigmatism (a cylindrical lens of an appropriate powerbeing worn)

[0172] Compound astigmatism (a combination of a cylindrical lens and aspherical lens being worn)

[0173] Irregular astigmatism (contact lenses being worn)

[0174] For example, as shown in FIG. 5, a database on the relationshipbetween the age and the accommodation power of the eyeball manages anaverage accommodation power written thereon corresponding to each age.

[0175] A starting optical eyeball model database has an optical eyeballmodel pre-constructed therein which has a median value in each age classrepresented on the vertical axis and a median value in each approximatelens power class represented on the horizontal axis. Accordingly, withthe vertical axis representing M classes and the horizontal axisrepresenting N classes, recorded and managed are M by N starting opticaleyeball models.

[0176] A visual image database writes thereon and manages the visualimages and sharpness scores of the subject before and/or after thecorrection by means of an eyeglass/contact lens.

[0177] Now, an explanation is given below to a method for measuringvision using the remote subjective vision measurement system 10.

[0178] First, a method for measuring an uncorrected eye will bedescribed.

[0179] Connecting the user client 1 to the electronic service center 2causes an ID code input window to be sent as a user authenticationwindow. The user authentication window prompts the user to input theuser authentication information. The user client 1 receives and displaysthe user authentication window and then allows the user authenticationinformation to be entered and sent to the electronic service center 2.

[0180] The user authentication information includes the password, theuser ID, etc.

[0181] The electronic service center 2 receives the user authenticationinformation, and in accordance therewith, the database management means232 and the user information management means 230 retrieve the userinformation database for authentication.

[0182] The electronic service center 2 allows the database managementmeans 232 to send a service menu window to the user client 1 as a membertop page.

[0183] The user client 1 receives and displays the service menu window.

[0184] Then, on the service menu window, the user clicks the“uncorrected eye vision measurement” to measure the vision of anuncorrected eye.

[0185] This causes the wearing condition input window to be sent fromthe electronic service center 2 to the user client 1 via the WWW server30. The wearing conditions include the purpose of wearing aneyeglass/contact lens (e.g., when the user wants to wear theeyeglass/contact lens, i.e., for viewing an object at hand, viewing anobject at a distance, or driving a car) and a viewing environment (e.g.,the range and distance of frequent viewing in daily life or thefrequency of working at a personal computer).

[0186] Furthermore, the user information input window is sent from theelectronic service center 2 via the WWW server 30.

[0187] As the information for identifying the user, the user informationinput window prompts the user to input user information includinggeneral attributes such as the user code, the user identifier (ID), theuser password, the address, the name, the birthday, and the telephonenumber; and data concerning the purpose of use, the near point distance,the far point distance, the age, the previous power, the sharpness ofvision of both eyes with the previous power, the balance between theright and left eyes with the previous power, the years of use of theprevious eyeglasses, the type of contact lenses (when used together),the desired corrected sharpness of vision, and any eye disease affectingthe vision.

[0188] Then, an uncorrected eye vision measurement window is sent fromthe electronic service center 2 to the user client 1 via the WWW server30.

[0189] First, the astigmatic axis determination chart shown in FIG. 6 isdisplayed, and the user checks any unevenness in viewing by varying thedistance within a range of 1 m.

[0190] The user views the uncorrected eye vision measurement window (notshown) by one eye with the other eye being covered with a hand. Theuncorrected eye vision measurement window shows an image or a viewedtarget to be gazed at with one eye.

[0191] Then, the user fixes his jaw to keep the distance constant fromthe uncorrected eye vision measurement window. For example, the user mayput his jaw on the palms of his hands to fix his face with the elbowsplaced on the desk.

[0192] The near point distance is then measured. The near point distancemeasurement checks how close the subject can approach the screen viewingit with ease. The face is kept stationary where the subject can see thewindow without blurring, and then the distance between the screen andthe eye is measured to provide the near point distance.

[0193] Thereafter, the far point distance is measured. The far pointdistance measurement checks how far the subject can go away from thescreen viewing the screen with ease. The face is kept stationary at themost distant position where the subject can see the window withoutblurring (the position at which blurring starts to occur), and then thedistance between the screen and the eye is measured to provide the farpoint distance.

[0194] A ruler or a yardstick is placed horizontally to measure thedistance between the screen and the eye for input.

[0195] Now, a method for determining the power of an eyeglass/contactlens will be described below with reference to the flowchart shown inFIG. 7.

[0196] First, as the information regarding the conditions of the eyes ofthe subject, the measured near point distance, the measured far pointdistance, the wearing conditions, and the age are entered at theinputting means 202 via the WWW browser. (The measured near pointdistance is provided by checking how close the subject can approach thescreen viewing the screen with ease, in which the face is keptstationary where the subject can see the window without blurring, andthen the distance between the screen and the eye is measured. Themeasured far point distance is provided by checking how far the subjectcan go away from the screen viewing the screen with ease, in which theface is kept stationary where the subject can see the window withoutblurring, and then the distance between the screen and the eye ismeasured. The wearing conditions include the purpose of wearing aneyeglass/contact lens, e.g., when the user wants to wear theeyeglass/contact lens, i.e., for viewing an object at hand, viewing adistant object, or driving a car, and a viewing environment, e.g., therange and distance of frequent viewing in daily life or the frequency ofworking at a personal computer).

[0197] The age relates to the accommodation power of the eye, inparticular, to the elasticity of the lens of the eye, the accommodationpower being decreased with advancing age (see FIG. 5). The accommodationpower decreases with advancing age as mentioned above. This isconceivably because the elasticity of the lens of the eye is reducedwith advancing age, thereby making it difficult to vary the refractivepower in response to distance.

[0198] It is also estimated that the accommodation power becomes weakerwith advancing age, but people at the same age have generally the sameaccommodation power.

[0199] For those who are nearsighted at their early ages, themeasurement of the near point distance tends to yield an error. Thus, acorrection table for correcting the error may be prepared in accordancewith the results of a vision test separately carried out so as tocorrect the error in the near point distance.

[0200] Then, the approximate lens power of an eyeglass/contact lens isdetermined in accordance with the age and the information regarding thenear point distance and the far point distance. The accommodationmidpoint position is calculated from the approximate lens power derivedfrom the far point distance and the near point distance. For example,assume that the far point distance is 1 m and the near point distance is25 cm. In this case, the lens power required for the correction at thefar point distance is −1.0 D (diopter), while the lens power requiredfor the correction at the near point distance is −4.0 D (diopters).Considering that the approximate lens power lies at the center of them,it is given by (−1-4)/2=−2.5 D.

[0201] The distance at this time is the reciprocal of the approximatelens power, which gives 40 cm. The distance 40 cm is considered to bethe accommodation midpoint position.

[0202] Then, the optical eyeball model determination means 204determines a starting optical eyeball model from the age and theapproximate lens power.

[0203] The starting optical eyeball model is an optical eyeball modelpre-constructed which has a median value in each age class representedon the vertical axis and a median value in each approximate lens powerclass represented on the horizontal axis. With the vertical axisrepresenting M classes and the horizontal axis representing N classes, Mby N starting optical eyeball models will be present.

[0204] That is, for example, employed is a table in which the verticalaxis represents the age class (e.g., at five year intervals up to twentyyears of age, and at 10 year intervals for 20 years of age or more) andthe vertical axis represents the approximate lens power (e.g., atintervals of 1.0 D). With this table, such a starting optical eyeballmodel is pre-constructed which takes the combination of median values ineach class (e.g., the 35 years of age and the lens power of the amountof correction required being −2.5 D).

[0205] The entering of the specific age and the approximate lens powerof the person allows for selecting one of the M by N starting opticaleyeball models.

[0206] The starting optical eyeball model selected is employed as aninitial value to perform automatic optical design processing forconstructing an optical eyeball model unique to the person.

[0207] When compared with automatic optical design processing thatemploys a single starting optical eyeball model independent of the ageand the approximate lens power, this starting optical eyeball modelconverges the automatic design processing more quickly at a higher speedof processing, making itself available on the Web. Furthermore, itprovides more reliable solutions (the optical dimensions for the optimalfocal power).

[0208] Now, a method for determining the starting optical eyeball modelis described.

[0209] (1) One combination is assumed between the approximate lens powerclasses and the age classes. It is assumed that the intermediate stateof human accommodation function is at the accommodation midpointposition, and the approximate lens power corrects the refractive powerof the human eye in the intermediate state. The accommodation midpointposition is determined from the approximate lens power.

[0210] (2) Using this starting optical eyeball model, a beam of light isspecifically entered to the eye from the accommodation midpoint positionto evaluate the state of convergence of the light beam on the retina. Toprovide the optimal convergence, the automatic optical design processingis performed varying the optical dimensions to determine the optimalsolutions (optical dimensions).

[0211] This is the same as the “human optical eyeball model constructionprocessing at the accommodation midpoint”, discussed later.

[0212] (3) Using a correlation table of average accommodation rangescorresponding to ages, and assuming an average accommodation rangeexists corresponding to an assumed age, the degrees of eyeballrefraction are derived at the upper and lower limits of theaccommodation range, based on which derived are the near point distanceand the far point distance.

[0213] (4) The starting optical eyeball model is checked for validity atthe accommodation limit (on the near point side) and at theaccommodation limit (on the far point side). If valid, the model isdetermined as the starting optical eyeball model. If the light is badlyconverged, the process goes back to (3) to perform the processing again.

[0214] (5) The aforementioned processing is executed M by N times,thereby preparing M by N starting optical eyeball models.

[0215] (6) An overall consideration is made to the optical dimensions ofthe M by N optical eyeball models mainly in terms of contradiction andcontinuity, and then modifications are made thereto. In some cases, theprocessing will be repeated from (2). In particular, the processing islikely repeated to determine the refractive index distribution of thelens of the eye.

[0216] Then, an optical eyeball model of the subject is constructed atthe accommodation midpoint.

[0217] In the construction of the optical eyeball model at theaccommodation midpoint, the automatic optical design calculation beginswith the aforementioned starting optical eyeball model to automaticallydetermine the optical dimensions of a human eyeball so as to provide theoptimal focal power.

[0218] As used herein, the automatic optical design calculation refersto the automatic process for determining optical dimensions by lightbeam tracking using an automatic lens design program. As a typicalexample of these techniques, the dumped least squares method isavailable, which is employed in this embodiment to perform the automaticaberration correction processing so as to provide the optimal focalpower.

[0219] The automatic aberration correction processing provides acorrection to satisfy a final performance condition (or a good focalpower condition in which a plurality of beams of light are impinged froman infinitesimal point object located at the accommodation midpointposition upon the pupil diameter (e.g., φ=3 mm) of the optical eyeballmodel at various heights of incidence to track the beams of light,thereby allowed to focus onto a point on the retina). Here, thecorrection is performed so as to minimize the sum of squares of theamount of deviation in position from the point of arrival of light onthe retina while the optical dimensions are being gradually varied. Incase the radius of curvature and the spacing between the surfaces ofeach lens were varied among the optical dimensions of the optical eyemodel for lenses having a spherical surface, and in case the radius ofcurvature of the reference spherical surface and the aspherical surfacecoefficient of the lenses were varied for lenses having an asphericalsurface, it was found that the solutions were quickly converged. Thus,this embodiment was designed to perform the automatic aberrationcorrection with the aforementioned optical dimensions employed asparameters in each of these cases.

[0220] Then, the model validity verifying means 206 is used to check thevalidity of the optical eyeball model at the accommodation limit (on thenear point side).

[0221] In this validity check, the eyeball refractive power is broughtup (UP) by the amount of accommodation power of a human eyeball, andthen the automatic optical design calculation is performed to confirm agood focal power.

[0222] As used herein, the “bringing up (UP) the eyeball refractivepower by the amount of accommodation power” means as follows.

[0223] Assuming that the far point distance is 1 m (−1.0 D) and the nearpoint distance is 25 cm (−4.0 D), the accommodation midpoint position is40 cm (−2.5 D) and an UP in the eyeball refractive power correspondingto the amount of correction of −1.5 D is required on the near point sidewith respect to the accommodation midpoint position.

[0224] As described above, an increase in eyeball refractive powercorresponding to this −1.5 D is provided as follows. That is, theoptical dimensions of the optical eyeball model are multiplied by(1+×b/a). Then, while the boundary conditions for the automatic opticaldesign are being controlled, a plurality of beams of light are impingedfrom an infinitesimal point object located at a near point distance of25 cm upon the pupil diameter (e.g., φ=3 mm) of the optical eyeballmodel at various heights of incidence to track the beams of light. Thus,the automatic optical design is performed while the optical dimensionsare being varied so as to focus the beams of light on a point on theretina.

[0225] Suppose that this has conceivably resulted in the convergence ofthe light on one point. In this case, it is determined that the opticalmodel has been successfully simulated at the accommodation limit, andthe optical eyeball model of the subject is valid at the accommodationmidpoint.

[0226] Then, the model validity verifying means 206 checks the validityof the optical eyeball model at the accommodation limit (on the farpoint side).

[0227] In the validity check, the eyeball refractive power is broughtdown (DOWN) by the amount of accommodation power of a human eyeball, andthen the automatic optical design calculation is performed to confirm agood focal power.

[0228] As used herein, the “bringing down (DOWN) the eyeball refractivepower by the amount of accommodation power” means as follows.

[0229] Assuming that the far point distance is 1 m (−1.0 D) and the nearpoint distance is 25 cm (−4.0 D), the accommodation midpoint position is40 cm (−2.5 D) and a DOWN in the eyeball refractive power correspondingto the amount of correction of +1.5 D is required on the far point sidewith respect to the accommodation midpoint position.

[0230] As described above, a decrease in eyeball refractive powercorresponding to this +1.5 D is provided as follows. That is, theoptical dimensions of the optical eyeball model are multiplied by(1−×b/a). Then, while the boundary conditions for the automatic opticaldesign are being controlled, a plurality of beams of light are impingedfrom an infinitesimal point object located at a far point distance of 1m upon the pupil diameter (e.g., φ=3 mm) of the optical eyeball model atvarious heights of incidence to track the beams of light. Thus, theautomatic optical design is performed while the optical dimensions arebeing varied so as to focus the beams of light on a point on the retina.

[0231] Suppose that this has conceivably resulted in the convergence ofthe light on one point. In this case, it is determined that the opticalmodel has been successfully simulated at the accommodation limit, andthe optical eyeball model of the subject is valid at the accommodationmidpoint.

[0232] Furthermore, the model validity verifying means 206 checks thevalidity of the optical eyeball model outside the accommodation limitson the near and far point sides, i.e., outside the range ofaccommodation of the eyeball.

[0233] Then, the optical eyeball dimension accommodation range definingmeans 208 finally determines the range of accommodation of the eyeballoptical dimensions for the optical eyeball model at the accommodationmidpoint position.

[0234] The optical eyeball model at the accommodation midpoint positionand the range of accommodation of the optical dimensions are determinedas follows.

[0235] The model validity verifying means 206 performs the processingfor checking the validity of the optical eyeball model at theaccommodation limit (on the near point side) and the model validityverifying means 206 performs the processing for checking the validity ofthe optical eyeball model at the accommodation limit (on the far pointside). These checks determines, as a result of the processing forconstructing an optical eyeball model of the person at the accommodationmidpoint, that the optical eyeball model is valid at the accommodationmidpoint position. The optical eyeball model is then used in the focalpower calculation processing, discussed later, which is accompanied byaccommodation at the three distances with the eye uncorrected, and thefocal power calculation processing which is accompanied by accommodationat the three distances with the eye corrected.

[0236] It can be said that the range of changes in optical dimensions atthe accommodation limits (in particular, the range of changes inthickness of the lens of the eye within which the lens of the eye ismade thinner or thicker, in the radius of curvature of the frontsurface, and in the radius of curvature of the rear surface) has alsobeen determined by the model validity verifying means 206 performing theprocessing for checking the validity of the optical eyeball model at theaccommodation limit (on the near point side) and the model validityverifying means 206 performing the processing for checking the validityof the optical eyeball model at the accommodation limit (on the farpoint side).

[0237] The determination of them makes it possible to simulate theaccommodation of the eye according to the distance to an object.

[0238] Then, the optical eyeball model image generating means 210 mayalso be used to display the image of the optical eyeball modeldetermined, e.g., by producing an eyeball cross-sectional view anddisplaying the description of its optical eyeball model at the sametime.

[0239] Then, the optical eyeball model focal power verifying means 212is used to calculate and verify the focal power that is accompanied bythe accommodation at the three distances with the eye of the subjectbeing uncorrected.

[0240] In the calculation above, the amount of an increase (UP) or adecrease (DOWN) in eyeball refractive power from the accommodationmidpoint position is determined according to the distance to an objectto perform the automatic optical design while the boundary conditionsare being controlled, like the model validity verifying means 206.

[0241] The optical dimensions determined as described above representthe condition of the eye in which the eyeball virtually performs focusaccommodation.

[0242] The calculation is repeated until no more improvement can be madein focal power, and the resulting optical dimensions are determined asthe best focal power at the distance to the object.

[0243] To evaluate the focal power, several hundreds of beams of lightequally dispersed are impinged from an infinitesimal point objectlocated at a certain distance upon the pupil diameter (e.g., φ=3 mm) ofthe optical eyeball model to track the beams of light, therebycalculating where the beams of light are focused on the retina. Toevaluate the degree of blurring, the two-dimensional Fourier transformis performed on the intensity distribution of a point image on theretina, thereby calculating the spatial frequency characteristics (OTF)to evaluate the image.

[0244] For the three distances, any three distances are selected atwhich the way of viewing is significantly varied. For example, they are0.3 m (near distance), 0.5 to 0.6 m (intermediate distance), and 5 m(far distance).

[0245] If the distance to the object is greater than to the far point,then the accommodation power at the far point distance is used to checkthe focal power.

[0246] If the distance to the object is less than to the near point,then the accommodation power at the near point distance is used to checkthe focal power.

[0247] If the distance to the object lies between the near point and thefar point, then the eyeball refractive power is varied by the amount ofaccommodation power at the midpoint to check the focal power.

[0248] Then, the optical eyeball model focal power verifying means 212is used to calculate and verify the focal power that is accompanied bythe accommodation at the three distances after the correction with aneyeglass/contact lens.

[0249] That is, an actual eyeglass lens (with known radii of curvatureof the front and rear surfaces of the lens and a known refractive indexof the glass material) is placed in front of the optical eyeball modelto perform a calculation like the focal power calculation processingwith the eye uncorrected.

[0250] From the approximate lens power and the wearing conditions, anappropriate virtual lens is determined to perform an optical simulationon the focal power with the eyeglass/contact lens being worn.

[0251] On the other hand, when the balance between the sharpness scoresat the three distances is badly kept, the lens power is slightly variedto perform the optical simulation again.

[0252] (A) Calculation of Sharpness Score

[0253] Now, the sharpness score generating means 216 is used to vary theoptical dimensions of the eye within the range of accommodation tocreate the condition in which the focal power is optimally provided,calculating the sharpness score at that time.

[0254] Here, the focal power is evaluated, thereby calculating thesharpness score several hundreds of beams of light equally dispersed areimpinged from an infinitesimal point object located at a certaindistance upon the pupil diameter (e.g., φ=3 mm) of the optical eyeballmodel to track the beams of light, thereby calculating where the beamsof light are focused on the retina. A value obtained by thetwo-dimensional Fourier transform being performed on the intensitydistribution of the point image is called the spatial frequencycharacteristics (OTF). Checking how the intensity is distributed on theretina makes it possible to evaluate the degree of blurring. The spatialfrequency is a value which represents the fineness of a stripe patternand is defined as the number of stripes per unit length.

[0255] For a visual system, it is represented by the number of stripesper visual angle of 1 degree. For example, assuming that the spacing ofthe stripes is w (degrees), it is given that u=1/w (cycles/deg). Thevalue of w used for the evaluation of blurring is found from theresolution of the retina, allowing the sharpness score to be calculatedbased on the value of u provided at that time.

[0256] Then, the lens power selecting means 218 is used to finallydetermine the lens to be recommended.

[0257] The visual image generating means 214 is then used to generatevisual images at the three distances before and after the correctionwith the recommended lens. That is, the ways of viewing are presentedfor the uncorrected eye and for the recommended lens being worn.Furthermore, the aforementioned sharpness score is presented anddisplayed in the visual image (as shown in FIG. 9).

[0258] (B) Generation or Selection of Visual Image

[0259] The visual image generating means 214 is used to prepare imagesat the three distances which are photographed at high resolution.

[0260] The N by N size smoothing filter processing is performed on theimages pixel by pixel to blur the images. The degree of blurring can beadjusted by the value of N (at a minimum of 3), filter weighting, andthe number of times of the processing.

[0261] The spatial frequency analysis is performed on the images thathave been filtered in order to determine the degree of blurring, whichis in turn associated with the sharpness score that has been determinedthrough the calculation of the sharpness score in (A) above.

[0262] Several images are prepared which correspond to some sharpnessscores. Furthermore, the score values are calculated which correspond tothe images obtained by the special smoothing filter processing beingperformed once on the prepared images.

[0263] The score value determined by the calculation of the sharpnessscore in (A) above is used to directly call the corresponding image fordisplay or to filter the image to display the resulting imagecorresponding to its sharpness score.

[0264] Furthermore, the visual image generating means 214 is used topresent viewed images at the three distances using a different lens forcomparison. That is, using a different lens power, an optical simulationis performed with an eyeglass/contact lens being worn.

[0265] Then, the optical dimensions are varied within the range ofaccommodation of the eyeball to create the condition in which an optimalfocal power is provided, thereby allowing the sharpness score at thattime to be calculated.

[0266] On the other hand, if the sharpness score has been calculated ata particular lens power by means of the lens power selecting means 218,then that data is employed.

[0267] The electronic service center 2 allows outputting means 22 tosend the viewed images produced as described above and the sharpnessscore to the user client 1 via the WWW server 30.

[0268] The electronic service center 2 also sends subjective visionmeasurement results separately prepared to the user client 1, allowingthe result to be displayed on a subjective vision measurement resultwindow. The subjective vision measurement results include the followingitems.

[0269] Included are DIST (indicative of a power for farsightedcondition), READ (indicative of a power for nearsighted condition), SPH(indicative of a spherical power), CYL (indicative of an astigmaticpower), AXIS (indicative of an axis), and P.D. (indicative of thedistance between the center of the right eye and that of the left eye,i.e., the distance between the pupils).

[0270] Both the power for farsighted condition and the power fornearsighted condition are expressed for the right eye (R•) and the lefteye (L•).

[0271] The current vision measurement with the automatic refractor isconsidered to provide the selection of a lens that optimizes the distantvision, in the case of which the lens is actually worn after themeasurement to adjust the lens power to be selected taking the wearingconditions into account. However, this invention makes it possible tofind the way of viewing at a plurality of distances with certain lensesbeing worn by means of the sharpness score. Thus, taking into accountthe wearing conditions which have been entered initially, the balancebetween the ways of viewing at the three distances can be considered topresent the optimum lens power available with comfort. That is, althoughthe subjective examination is currently essential by which the actualway of viewing is confirmed, it can be eliminated. This is preferablyavailable for on-line shopping.

[0272] This embodiment has been designed to construct an optical eyeballmodel at the accommodation midpoint of the subject; however, withoutbeing limited thereto, it may also be designed to construct an opticaleyeball model at a given point between the near point distance and thefar point distance of the subject. In this case, the accommodation powercan be distributed to the strained side or the relaxed side according tothe accommodation position at which the optical eyeball model has beenconstructed, thereby constructing an optical eyeball model at theaccommodation limit on the near point side or the far point side.

[0273] The aforementioned embodiment employed the starting opticaleyeball models, each of which was pre-constructed based on the medianvalue in each of M classes of age and N classes of approximate lenspower, as the initial value used in the optical automatic designprocessing for constructing the optical eyeball model unique to asubject. However, without being limited thereto, such an optical eyeballmodel that is most suitable to the data entered by the subject may alsobe employed as the initial value for the optical automatic designprocessing. In this case, the amount of difference is added to orsubtracted from the median value in a class in accordance with the ageentered by the subject and the approximate lens power calculated,thereby allowing the optical eyeball model corresponding to thecondition of the eyeball of the subject to be employed as the initialvalue. This makes it possible to perform the automatic aberrationcorrection in less time than in the case where the automatic aberrationcorrection is performed using the starting optical eyeball model thathas been pre-constructed based on the median values.

[0274] Furthermore, this embodiment determined the value of w used forthe evaluation of blurring from the resolution of the retina and allowedthe sharpness score to be calculated from the value of u provided then;however, without being limited thereto, other techniques may also beemployed to calculate the sharpness score. For example, the spatialfrequency of an incident light beam is varied to find the value of aspatial frequency that provides an OTF value of 70%. In this case, thespatial frequency of the incident light beam is varied at equalintervals within a certain range to determine the spatial frequencywhich provides an OTF value of 70% with the minimum spatial frequencybeing zero and the maximum spatial frequency being 100, therebyproviding the sharpness score that is developed from zero to 100.

[0275] This embodiment allows the visual image generated by the visualimage generating means 216 to be viewed by the subject as it is;however, without being limited thereto, the degree of blurring of theimage may be corrected and then the resulting image may be presented tothe subject. This is because of the following reason. That is, humanbeing tends to feel as if he/she clearly sees even an actually blurredvisual image when he/she views an object or scenery which he/she hasonce viewed before or which is similar to it, because the visualinformation of human being is corrected according to the memory of theobject or the scenery that he/she has seen once before. Therefore, morespecifically, a number of subjects verify the difference between theimage produced by the visual image generating means 216 and the degreeof blurring that the subjects feel when actually viewing it. Acorrection coefficient table is prepared in accordance with the resultsof the verification to present the image to a subject based on theresult obtained by correcting the degree of blurring according to thecorrection coefficient table.

[0276] On the other hand, this embodiment is designed such that thesubject uses the uncorrected eye vision measurement window to actuallymeasure how far the subject can stay away from the screen in order toinput the data on the far point distance for calculating the approximatelens power; however, without being limited thereto, the far point visionmay also be measured to calculate the far point distance.

[0277]FIG. 11 illustrates another embodiment which determines theastigmatic axis, measures the near point distances and measures the farpoint vision, including the processing for calculating the far pointdistance from the measured far point vision. First, the process displaysa subject attribute input window for acquiring the attributes of asubject (S10), and then acquires the attributes entered by the subjectto store them as the subject data (S12). The attributes of the subjectinclude the personal information such as the age, the sex, and theheight, and wearing condition information regarding the place where theeyeglasses or the contact lenses are mainly used. FIG. 12 is an exampleof a display window for acquiring personal information, FIG. 13 being anexample of a display window for acquiring wearing conditions. Here, itis assumed that the “reading” and “deskwork” in the wearing conditionsare for near distances, the “personal computer” for intermediatedistances, and the “driving cars” for far distances.

[0278] Then, the process displays an astigmatic axis determination chartfor determining the astigmatic axis (S14) to acquire the orientationthat the subject has selected and store it as selected orientation data(S16). FIG. 14 is an explanatory view illustrating an example of awindow for use with the astigmatic axis determination, FIG. 15 showingan example of the astigmatic axis determination window.

[0279] As illustrated, the astigmatic axis determination chart is madeup of four groups of a plurality of parallel lines, each group havinglines extended in one orientation at an angle of 45 degrees, 90 degrees,135 degrees, and 180 degrees, respectively. A subject with astigmatismexperiences the orientation which provides the sharper viewing and theorientations which provide the less-sharper blurry viewing, and isprompted to click on the zone in the orientation that provides adifferent viewing. The process prompts the subject to select theorientation that provides a different viewing as mentioned above. Thisis because astigmatism may possibly cause a different orientation toprovide the sharper viewing depending on the distance to the object, andthus employing the orientation that provides the sharper viewing at thefirst gaze would possibly cause an error in determination of theastigmatic axis. Therefore, the present invention is designed not todetermine the main axis of the astigmatic axis at this stage but to makeit clearly defined by determining the far point distance later.

[0280] In principle, a subject without astigmatism is probably providedwith the same viewing in all the orientations. Thus, the subject whoclicks on “All are viewed in the same way” or “Indistinguishable” isconsidered to have no astigmatism and undergoes the followingmeasurements only in the horizontal orientation.

[0281] The astigmatic axis determination chart has the background ingreen and the lines in black, with the width of the lines having twopixels and the width between the lines having three pixels. A backgroundcolor of white causes a miosis and a greater depth of field in the eyesdue to its excessive brightness, thus raising a problem of providingreduced difference in the way of viewing the four zones. This is why theeye-friendly green base color is used to reduce brightness. A color ofblack was employed as the color of the lines because a number ofsubjects who underwent an eye examination experiment determinedconsequently that black could be viewed with ease. The width of thelines has at least two pixels because particularly in the case of a CRTdisplay, one pixel may provide a different viewing between thehorizontal/vertical and the diagonal direction due to the occurrence offocus blurring caused by the electron gun. The width between the lineswas so set that the spacing between the lines could be recognized from adistance of 1 m because an extremely short distance to the chart in theastigmatism determination would vary the astigmatic axis, possiblyresulting in an error in the determination. A vision of 1.0 (an angle ofview of 0.1 degrees) indicates the capability of distinguishing a slitof 0.29 mm at a distance of 1 m, which generally corresponds to onepixel on a 14-inch liquid crystal display or a 17-inch CRT. Therefore,two pixels correspond to a vision of about 0.5. However, since those whotake the eye test need eyeglasses, the spacing was further expanded tohave three pixels.

[0282] On the other hand, the four orientations were provided for theastigmatic axis because of the following reasons. That is, this makes itpossible to select sufficiently practical eyeglasses or contact lenseseven using the four orientations, and the determination needs to be madeas easily as possible without any error because the subject makes thedetermination by himself or herself.

[0283] Then, to measure the far point vision in the selected orientationthat has been selected by the subject, the process displays the visionmeasurement chart for the selected orientation (S18) to acquire theviewing limit selected by the subject, which is then stored as firstviewing limit data (S20). FIG. 16 is an explanatory view illustrating anexample of a window for a far point vision measurement, FIG. 17 showingan example of the far point vision measurement window.

[0284] As illustrated, the vision measurement chart is a light and darkline image made up of three black lines and two white lines of a certainline width, a plurality of the charts being displayed in each of whichthe width of the lines are varied in I steps (from about 10 steps to 20steps) corresponding to vision. On the vision measurement charts, thesubject is prompted to click on the smallest mark that the subject candistinguish the three lines. Since the subject is allowed to select themark that provides the viewing of three lines as described above, thesubject can make a determination more easily when compared with theLandoldt ring that is viewed to visually distinguish a single gap.

[0285] The subject is urged to measure the far point vision at a reachfrom the computer screen. This is because the length of the arm isproportional in length to the height, and thus the distance between thesubject and the chart can be predicted in accordance with the data onthe height entered in advance.

[0286] As described above, the measurement can be conveniently carriedout because the subject does not need to measure the distance to thecomputer screen or adjust the window display size.

[0287] Likewise, to measure the far point vision in the orientationperpendicular to the selected orientation selected by the subject, theprocess displays the vision measurement chart in the orientationperpendicular to the selected orientation (S22), and the viewing limitselected by the subject is acquired and stored as second viewing limitdata (S24).

[0288] Then, to measure the near point distance in the orientationselected by the subject, the process displays a near point distancemeasurement chart in the selected orientation (S26) to store the nearpoint distance entered by the subject as the first near point distancedata (S28). FIG. 18 is an explanatory view illustrating an example of awindow for a near point distance measurement, FIG. 19 showing an exampleof the near point measurement window.

[0289] As illustrated, the near point distance measurement chart hasthree black lines provided in a green background. The message on thescreen urges first the subject to come as close to the screen aspossible and then go away therefrom to a position at which the subjectcan clearly see the three lines and measures the distance between theeyes and the screen, thereafter prompting the subject to input thedistance in centimeters.

[0290] The near point distance measurement chart employs thinner linescompared with the aforementioned vision measurement chart because thechart is viewed in close proximity to the computer screen. However,because of the difference in resolution due to the age, thin lines areused for the youth and slightly bolder lines are used for the middleaged and the elderly people.

[0291] To measure the near point distance in the orientationperpendicular to the selected orientation selected by the subject, theprocess displays a near point distance measurement chart in the selectedorientation (S30) to store the near point distance entered by thesubject as the second near point distance data (S32).

[0292] Then, the process determines the far point distance from thefirst viewing limit data, the first near point distance data, and thesubject limit data to store the resulting distance as the first farpoint distance data (S34). Likewise, the process determines the farpoint distance from the second viewing limit data, the second near pointdistance data, and the subject limit data to store the resultingdistance as the second far point distance data (S36).

[0293] The far point distance is operated using a neural network that anumber of subjects have taught in advance. FIG. 20 is a viewillustrating an exemplary configuration of a neural network foroperating the far point distance. As illustrated, the input layer has Isteps of far point vision (the viewing limit selected by the subject onthe vision measurement chart), J steps of near point distance (the nearpoint distance measured by the subject on the near point distancemeasurement chart), and K steps of subject attributes (the age, the sex,and the height), while the output layer has N steps of far pointdistance. The age and sex are employed as parameters because theaccommodation power of the eyes of the subject is varied due to them.The height, as described above, that is proportional to the length ofthe arm is used as a substitute parameter in order to adjust thedistance between the subject and the screen to the length of the arm. Asthe method of learning, employed is the so-called back-propagationmethod.

[0294] Here, to make the conversion into the lens power easier, the nearpoint distance of the input parameters and the far point distanceresulted from the operation are each converted for handling to the valueD (diopter) or the reciprocal of the distance measured in meters.

[0295] The neural network was designed to produce two independentlearning models in the selected orientation of the astigmatic axis andthe orientation perpendicular to the selected orientation to performcalculations for each of them separately.

[0296] Since different types of displays provide different ways ofviewing the screens, the operation was performed using neural networksthat had been separately taught depending on the display being eitherthe liquid crystal display or the CRT.

[0297] The aforementioned embodiments are designed to calculate theapproximate lens power from the far point distance; however, withoutbeing limited thereto, the approximate lens power may also be determinedfrom the far point vision entered. In this case, a corresponding tableis used, which is prepared in accordance with statistical data andstores the approximate lens power corresponding to the value of the farpoint vision, to determine the approximate lens power based on thecorresponding table.

[0298] Furthermore, in the process of determining the lens power, theaforementioned embodiments verify the focal power of the optical eyeballmodels at the three distances, i.e., the near distance (0.3 m), theintermediate distance (0.5 to 0.6 m), and the far distance (5 m);however, without being limited thereto, the focal power may also beverified at a distance other than those distances and may not always beverified for all of the near distance, the intermediate distance, andthe far distance.

[0299] Industrial Applicability

[0300] As described above, the present invention constructs the opticaleyeball model unique to a subject, thus making it possible to determinethe power of an eyeglass/contact lens that is suitable for anindividual.

1. (Amended) A system for determining an eyeglass/contact lens power,comprising: inputting means for entering information on a condition of asubject's eye; means for determining an optical eyeball modelcorresponding to the information on the eye condition entered throughsaid inputting means; and means for selecting a lens power for verifyinga focal power of an eyeglass/contact lens worn by the subject using theoptical eyeball model determined by said optical eyeball modeldetermining means, wherein said optical eyeball model determining meanshas means for verifying validity of the optical eyeball model at a givenaccommodation point between a near point distance and a far pointdistance of the subject.
 2. The system for determining aneyeglass/contact lens power according to claim 1, wherein said inputtingmeans includes means for displaying an astigmatic axis measurement chartto measure an astigmatic axis.
 3. The system for determining aneyeglass/contact lens power according to claim 1 or 2, wherein saidinputting means includes means for displaying a far point visionmeasurement chart to measure far point vision.
 4. The system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 3, wherein said inputting means includes means fordisplaying a near point distance measurement chart to measure a nearpoint distance.
 5. The system for determining an eyeglass/contact lenspower according to claim 3 or 4, wherein said inputting means has meansfor calculating a far point distance from the far point vision measured.6. The system for determining an eyeglass/contact lens power accordingto claim 5, wherein said inputting means has means for determining anapproximate lens power from said far point distance calculated.
 7. Thesystem for determining an eyeglass/contact lens power according to anyone of claims 1 to 6, wherein said optical eyeball model simulates eachlayer of an anterior cortex, a nucleoplasm, and a posterior cortex ofthe lens of the eye using a combination of plurality of lenses,respectively.
 8. The system for determining an eyeglass/contact lenspower according to any one of claims 1 to 7, wherein said opticaleyeball model has a characteristic that a refractive index of each ofsaid lenses simulating the lens of the eye is decreased with a distancefrom the center of the lens.
 9. The system for determining aneyeglass/contact lens power according to claim 8, wherein said opticaleyeball model has a refractive index distribution characteristic thatthe refractive index of each of said lenses simulating the lens of theeye is expressed by (a refractive index at the center of the lens)−((thesquare of a straight distance from the lens center)/(a refractive indexdistribution coefficient)).
 10. The system for determining aneyeglass/contact lens power according to any one of claims 7 to 9,wherein the refractive index distribution coefficient of each lenssimulating the lens of the eye is decreased with the distance from thecenter of said plurality of lenses in a direction of the optical axissimulating the lens of the eye to the direction of the optical axis. 11.The system for determining an eyeglass/contact lens power according toany one of claims 7 to 10, wherein said optical eyeball model calculatesoptical dimensions using a power distribution coefficient describing thedistribution of accommodation power per unit length of each lenssimulating the lens of the eye.
 12. The system for determining aneyeglass/contact lens power according to any one of claims 1 to 11,wherein said means for determining an optical eyeball model determines astarting optical eyeball model in accordance with an age of the subjectand information on the eye such as an approximate lens power 13.(Deleted)
 14. (Amended) The system for determining an eyeglass/contactlens power according to any one of claims 1 to 12, wherein said givenaccommodation point between the entered near point distance and the farpoint distance of the subject includes an accommodation midpointcalculated from the near point distance and the far point distance ofthe subject.
 15. (Amended) The system for determining aneyeglass/contact lens power according to any one of claims 1 to 14,wherein said means for determining an optical eyeball model performsautomatic aberration correction processing by employing a radius ofcurvature and an eccentricity of the aspherical surface of each lenssimulating said lens of the eye as parameters.
 16. The system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 15, wherein said means for determining an optical eyeballmodel includes means for verifying validity of the optical eyeball modelat an accommodation limit on a near point side and/or a far point side.17. The system for determining an eyeglass/contact lens power accordingto any one of claims 1 to 16, wherein said means for determining anoptical eyeball model displays an image of the optical eyeball modeldetermined.
 18. The system for determining an eyeglass/contact lenspower according to any one of claims 1 to 17, wherein said means forselecting a lens power has a function to verify the focal power at asingle distance or a plurality of distances defined according to usage.19. The system for determining an eyeglass/contact lens power accordingto any one of claims 1 to 18, wherein said means for selecting a lenspower has a function to verify by comparison the focal power of theoptical eyeball model for an uncorrected eye.
 20. The system fordetermining an eyeglass/contact lens power according to any one ofclaims 1 to 19, wherein said means for selecting a lens power includesmeans for calculating a sharpness score indicative of the degree ofblurring in a visual image viewed by said optical eyeball model.
 21. Thesystem for determining an eyeglass/contact lens power according to anyone of claims 1 to 20, wherein said means for selecting a lens powerincludes means for presenting a simulated visual image viewed by saidoptical eyeball model.
 22. (Amended) A method for determining aneyeglass/contact lens power, comprising steps of: collecting informationon a condition of a subject's eye; determining an optical eyeball modelcorresponding to the information on the eye condition collected in saidcollecting step; and verifying a focal power of an eyeglass/contact lensworn by the subject using the optical eyeball model determined in saidstep of determining an optical eyeball model to select a lens power,wherein said step of determining an optical eyeball model has a step ofverifying validity of the optical eyeball model at a given accommodationpoint between a near point distance and a far point distance of thesubject.
 23. The method for determining an eyeglass/contact lens poweraccording to claim 22, wherein said collecting step includes a step ofdisplaying an astigmatic axis measurement chart to measure an astigmaticaxis.
 24. The method for determining an eyeglass/contact lens poweraccording to claim 22 or 23, wherein said collecting step includes astep of displaying a far point vision measurement chart to measure farpoint vision.
 25. The method for determining an eyeglass/contact lenspower according to any one of claims 22 to 24, wherein said collectingstep includes a step of displaying a near point distance measurementchart to measure a near point distance.
 26. The method for determiningan eyeglass/contact lens power according to claim 24 or 25, wherein saidcollecting step has a step of calculating a far point distance from saidfar point vision measured.
 27. The method for determining aneyeglass/contact lens power according to claim 26, wherein saidcollecting step has the step of determining an approximate lens powerfrom said far point distance calculated.
 28. The method for determiningan eyeglass/contact lens power according to any one of claims 22 to 27,wherein said optical eyeball model simulates each layer of an anteriorcortex, a nucleoplasm, and an posterior cortex of the lens of the eyeusing a combination of plurality of lenses, respectively.
 29. The methodfor determining an eyeglass/contact lens power according to any one ofclaims 22 to 28, wherein said optical eyeball model has a characteristicthat a refractive index of each of said lenses simulating the lens ofthe eye is decreased with a distance from the center of the lens. 30.The method for determining an eyeglass/contact lens power according toclaim 29, wherein said optical eyeball model has a refractive indexdistribution characteristic that the refractive index of each of saidlenses simulating the lens of the eye is expressed by (a refractiveindex at the center of the lens)−((the square of a straight distancefrom the lens center)/(a refractive index distribution coefficient)).31. The method for determining an eyeglass/contact lens power accordingto any one of claims 28 to 30, wherein said refractive indexdistribution coefficient of each lens simulating the lens of the eye isdecreased with the distance from the center of the plurality of lensesin a direction of the optical axis simulating the lens of the eye to thedirection of the optical axis.
 32. The method for determining aneyeglass/contact lens power according to any one of claims 28 to 31,wherein said optical eyeball model calculates optical dimensions using apower distribution coefficient describing the distribution ofaccommodation power per unit length of each lens simulating the lens ofthe eye.
 33. The method for determining an eyeglass/contact lens poweraccording to any one of claims 22 to 32, wherein said step ofdetermining an optical eyeball model determines a starting opticaleyeball model in accordance with an age of the subject and informationon the eye such as an approximate lens power.
 34. (Deleted) 35.(Amended) The method for determining an eyeglass/contact lens poweraccording to any one of claims 22 to 33, wherein said givenaccommodation point between the entered near point distance and farpoint distance of the subject includes an accommodation midpointcalculated from the near point distance and the far point distance ofthe subject.
 36. (Amended) The method for determining aneyeglass/contact lens power according to any one of claims 1 to 35,wherein said step of determining an optical eyeball model performsautomatic aberration correction processing by employing a radius ofcurvature and the eccentricity of an aspherical surface of each lenssimulating said lens of the eye as parameters.
 37. The method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 36, wherein said step of determining an optical eyeballmodel includes a step of verifying validity of the optical eyeball modelat an accommodation limit on a near point side and/or a far point side.38. The method for determining an eyeglass/contact lens power accordingto any one of claims 22 to 37, wherein said step of determining anoptical eyeball model displays an image of the optical eyeball modeldetermined.
 39. The method for determining an eyeglass/contact lenspower according to any one of claims 22 to 38, wherein said step ofselecting a lens power has a step of verifying the focal power at asingle distance or a plurality of distances defined according to usage.40. The method for determining an eyeglass/contact lens power accordingto any one of claims 22 to 39, wherein said step of selecting a lenspower has a step of verifying by comparison the focal power of theoptical eyeball model for an uncorrected eye.
 41. The method fordetermining an eyeglass/contact lens power according to any one ofclaims 22 to 40, wherein said step of selecting a lens power includes astep of calculating a sharpness score indicative of the degree ofblurring in a visual image viewed by said optical eyeball model.
 42. Themethod for determining an eyeglass/contact lens power according to anyone of claims 22 to 41, wherein said step of selecting a lens powerincludes a step of presenting a simulated visual image viewed by saidoptical eyeball model.